A communication technology called Evolved UTRA (E-UTRA) is being developed as a successor to W-CDMA and HSDPA. E-UTRA is a radio access technology that flexibly supports multiple bandwidths. Specifically, E-UTRA supports bandwidths from 1.25 MHz up to 20 MHz while maintaining compatibility with the existing 3G technology.
In the current W-CDMA, a preamble of a random access channel (RACH), which is a contention-based channel and is used to initially establish an uplink connection, is transmitted within a system by a combination of code division multiplexing and time division multiplexing.
For example, when users are multiplexed by code division multiplexing as shown in FIG. 1A, a terminal can select any signature from multiple signatures (codes) available.
On the other hand, when users are multiplexed by time division multiplexing as shown in FIG. 1B, a terminal can select any access slot from multiple access slots available.
Random access methods in W-CDMA are described, for example, in “W-CDMA Mobile Communication System”, Keizo Tachikawa, Maruzen Co. Ltd., June 2001, pp. 130-134.